The present invention relates to couplings for conduits and pipes and, more specifically, to a coupling assembly for joining the threaded ends of a pair of lengths of conduit in coaxial, abutting relationship.
It is a conventional practice in many types of pipe or conduit systems, and particularly in electrical systems employing tubular conduits, to connect a number of lengths of conduit in end-to-end relation through means of couplings so as to form a continuous conduit system as necessary for a particular application. In the case of thin wall conduit, which is primarily employed for encasing electrical cable or conductor wires in applications where the conduit will not be subjected to large stresses, compression fittings or set screw couplings may be employed. The conduit is generally available in different lengths, commonly 10 and 20 foot lengths, and may be quite readily formed to various bend contours and coupled end-to-end through the compression couplings or set screw couplings.
Another type of conduit which is particularly useful in commercial and industrial applications is generally termed rigid pipe or conduit. Such conduit may, for example, range up to 21/2 inches or greater in outer diameter and may have a wall thickness of 0.100 inch or greater which facilitates forming of external threads on the opposite ends of each length of conduit to enable their connection in end-to-end relation. As with thin wall conduits, the rigid pipe or conduit is also conventionally made in lengths of up to 10 to 20 feet long. Due to their relative weight, the rigid pipe lengths are not as readily manipulated during installation and are frequently installed where access is relatively limited so that rotation of the individual lengths, may be quite difficult, if not impossible.
One known technique for connecting lengths of rigid pipe or conduit in end-to-end relation is to provide generally V-shaped external pipe threads of standard size on the opposite ends of each length or section of conduit and then connect the desired number of conduit lengths in end-to-end relation through couplings having internal pipe threads therein which enable threaded connection with adjacent ends of conduit to form a structurally sound connection or coupling. A major drawback in this technique is that the coupling must be threaded onto one conduit section or length followed by relative movement between this conduit section and the conduit section to which it is to be coupled so that the conduit sections are in axial alignment. This generally requires relative longitudinal movement between adjacent conduit sections with simultaneous relative rotation therebetween to effect threaded engagement between the second conduit section and the coupling. Should the need subsequently arise to replace an intermediate section or length of conduit, either a length of the conduit or one or more couplings, or both the conduit and the couplings, must be destroyed in order to effect disassembly.
One recently proposed conduit coupling assembly permits lengths of conduit to be joined quickly. Furthermore, if replacement of a component of a completed system should be required, the coupling assembly allows disassembly of the system without adjacent lengths of conduit undergoing substantial relative longitudinal movement and without any need to rotate one of the lengths of conduit. This coupling assembly includes an outer coupling having ends and a bore extending therebetween for slidably, rotatably retaining an inner abutment ring having an inner thread so that the ring can be threaded onto the end portion of one of the lengths of conduit. This threading is accomplished by using the outer coupling as, in effect, a wrench. The abutment ring has a special annular lip having a slot for receiving the inward extension of a set screw received in a threaded aperture through the outer coupling. After installation of the abutment ring, the set screw is removed or adjusted so as not to interfere with sliding of the outer coupling relative to the abutment ring. It will be appreciated that this coupling system requires specially manufactured components and requires threading and unthreading of the set screw. For a more complete description of this coupling assembly and its operation, reference may be made to commonly assigned U.S. Pat. No. 4,258,936 to Goldberg.